The physico-chemical properties of soymilk particles were investigated as a function of concentration of protein in soymilk. Soymilk samples were prepared using different water-to-protein ratios, resulting in 4 %, 5 % and 7 % protein content. The soymilk particles were not significantly different in their protein composition, surface hydrophobicity and intrinsic fluorescence; however, their gamma-potential and particle size were affected by protein concentration. Using a relation between the effective refractive index of soymilk and the turbidity parameter determined experimentally using diffusing wave spectroscopy, it was possible to estimate, for the first time, a voluminosity of 4.11 mL/g and a refractive index of 1.388 for the colloidal particles. This allowed conversion of protein content to volume fraction, and comparison of the experimental data collected by diffusing wave spectroscopy, rheology and ultrasonic spectroscopy with theoretical models.
Ringgenberg, E., M. Corredig, M. Alexander